Tyre vulcanisation mould with blocking members moundted in venting bores

ABSTRACT

The invention relates to a vulcanization mold for producing rubber goods, especially vehicle tires. Said mold has a number of deairing holes into which blocking mechanisms are introduced. The blocking mechanisms ensure, especially by means of the air duct being bent, that the air can be drained without any disadvantageous flash being produced. In a second embodiment, the blocking mechanisms forms a two-part valve with the central body. In this case, the blocking mechanism has an elastically deformable planar area placed on the inside of the mold which acts at least essentially as a seal in conjunction with the central body when impinged upon by the surface of the blank.

[0001] The invention relates to a vulcanisation mould for themanufacture of technical rubber products, in particular for themanufacture of vehicle tires, comprising a plurality of venting bores ineach of which there is provided a blocking member, which at leastsubstantially blocks the penetration of blank material.

[0002] Vulcanisation moulds of this kind are, for example, known fromU.S. Pat. No. 4,347,212 or from the German patent specification 195 43276 C1.

[0003] The purpose of the venting bores, of which several thousands canbe provided in one vulcanisation mould, is to ensure a problem-freeventing of all regions of the vulcanisation mould provided with treadpattern forming webs in order to ensure that the tire blank canaccurately contact the form-giving tools or webs of the vulcanisationmould from the inside during the inflation process and that suchaccurate contact against the mould is not hindered by air inclusions.

[0004] An undesired disadvantage of the existing vent bores lies in thefact that rubber enters into these bores, which normally have a diameterof 0.7 to 1.5 mm, and the so-formed shoots give the finished tire abrush-like or hedgehog-like appearance. Various techniques areadmittedly known to remove these undesired shoots; however, all thesetechniques cause extra work and considerable costs.

[0005] In order to avoid the undesired shoots it is known to insertvalves into the venting bores which are closed by the approachingsurface of the blank and which open again during demoulding. Thedisadvantage of valves of this kind which have hitherto been used intire vulcanisation moulds lies above all in the fact that they arecomplicated as a result of their multi-part construction and that a coilspring is required to ensure a defined closing and opening process, withthe coil spring always having, as far as possible, the samecharacteristic for the large number of valves that are required. Theextremely small dimensions of these valves make it more difficult toensure practically identical characteristics.

[0006] The object of the invention is to provide a ventablevulcanisation mould with blocking members which are particularly simpleand thus economically designed, which can be installed and removedwithout problem and rapidly and which ensure a high operationalreliability.

[0007] This object is satisfied in accordance with the inventionessentially in that each blocking member includes a central body, inparticular a pin-like central body, which can be fixed in the respectivevent bore in force-locked manner, and also a sealing part connected tothe central body, with the sealing part having a surface region at theinner side¹ of the mould and substantially flush with it, which isprovided with at least one aperture and forms, together with themould-side end face of the central body at least one flowpath for theair, which is pronouncedly angled following the aperture.

[0008] Through the special design of the blocking member, which can beof one-piece or two-piece construction, it is possible to stop the blankmaterial which meets the blocking members without any movable elementsand simply as a result of the guidance of the air flow and to preventany form of disturbing penetration of blank material into the airdischarge passages that are formed, which would lead to shoots at thefinished product, which in turn has the consequence that on opening themould no rubber material remains in the specially formed air dischargepassages and could block the latter.

[0009] The absence of any movable elements, such as are present whenusing valves in the form of movable valve stems, leads to a highoperational reliability and, above all, to the fact that no damagearises during cleaning of the moulds, which is frequently effected byblasting them with ice crystals, which could make the blocking membersunsuitable for use. A further advantageous consequence of the design ofthe blocking members in accordance with the invention is the fact thatthe mould cleaning cycles can be substantially extended because of thelargely avoided danger of blocking members becoming ineffective throughcontamination.

[0010] When the blocking member of the invention is of two-partconstruction, a resilient latching of the sealing part to the centralbody preferably takes place. For this purpose, parts of the clampinglimbs which are intended for the fixation of the central body in themould bores and which are connected to the disc-like blocking surfaceare cranked inwardly in the form of coupling lugs and engage behindsupport projections on the central body so that a snap-in latchconnection is provided.

[0011] The blocking members formed in accordance with the invention canbe simply and rapidly positioned accurately in bores of the respectivemould, since for this it is only necessary to press the blocking membersinto the bores and the end position is achieved when the edge of thedisc-like blocking surface comes into contact with the wall of themould.

[0012] The blocking member of the invention accordingly operates in themanner of a nozzle with a specially shaped air guidance which preventsthe formation of mould shoots, for which purpose, on the one hand, theminimal dimensions of the existing air guidance channels and, on theother hand, the angled shape of these air guidance channels ischaracteristic.

[0013] Further advantageous embodiments of the invention are set forthin the subordinate claims 2 to 13.

[0014] In accordance with a second embodiment variant, the blockingmember is movable at least in the sense that it has an elasticallydeformable surface region at the inside of the mould. This surfacecooperates in an at least substantially sealing manner with the centralbody on being loaded by the surface of the blank. The blocking memberthus forms a two-part valve with the central body in accordance withthis embodiment.

[0015] In other words, the object is satisfied in accordance with theinvention in a second basic way by a vulcanisation mould for themanufacture of vehicle tires having a plurality of venting bores, ineach of which a valve is mounted and designed in such a way that it isat least substantially closed by the approaching surface of the blankand is opened again on demoulding, with the special characteristic thateach valve is of two-part design and includes a central body, inparticular a pin-like central body, which can be fixed in the respectiveventing bore, and also a sealing part which is releasably connected tothe central body and which has at least one elastically deformablesurface region disposed at the inner side of the mould, which cooperatesin an at least substantially sealing manner with the central body onbeing loaded by the surface of the blank.

[0016] Even though a movement of the surface region of the blockingmember disposed at the inner side of the mould occurs in the sense of anelastic deformation thereof in this embodiment variant in order toachieve a complete sealing and therefore a valve function, the degree ofmovement is relatively small and cannot be compared with the previouslyknown embodiments with valve tappets. With this second embodimentvariant, practically all advantages of the first embodiment variant canthus be achieved, with, however, the said first embodiment variant inaccordance with FIGS. 1 to 3 representing the best embodiment in theopinion of the applicant.

[0017] Not only is a substantial simplification of the construction ofthe valve achieved through the integration of the spring function intoone of the two components of the valve and through the avoidance of theneed to use an individual coil spring, which is achieved hereby, butrather the operational reliability is increased and the handling madeeasier.

[0018] The central body is of substantially cylindrical shape and has adiameter which is smaller in comparison to the diameter of the ventingbore. It can be fixed by clamping elements which are provided on thecentral body or on the sealing part in the respective venting bore,while forming air passages. Depending on the arrangement of the clampingelements on the central body or on the sealing part, two differentembodiments of venting valves arise which are, however, equivalent withrespect to their function. Since they each only consist of two parts, anadequately large air throughflow cross-section is present and closingand opening procedures take place in a predeterminable and reliablemanner as a result of the defined spring force.

[0019] Valves formed in accordance with the invention can bemanufactured of the most diverse materials, in particular of sheet metalspring material, die-cast aluminium or zinc, ceramic, sintered metalsand also of injection-moulded parts of appropriately suited metals orcorresponding temperature-resistant plastics.

[0020] Particularly favourable embodiments of this second variant of theembodiment of the invention are given in the subordinate claims 15 to29.

[0021] The invention will be explained in the following by way of anembodiment with reference to the drawings in which are shown:

[0022]FIG. 1 a perspective representation of a first embodiment of ablocking member in accordance with the invention;

[0023]FIG. 2 a perspective representation of the central body of theblocking member of FIG. 1;

[0024]FIG. 3 a perspective representation of the sealing part of theblocking member of FIG. 1;

[0025]FIG. 4 a perspective representation of a second embodiment of theinvention in the form of a venting valve;

[0026]FIG. 5 a perspective representation of the central body of thevalve in accordance with FIG. 4;

[0027]FIG. 6 a perspective representation of the sealing part of a valvein accordance with FIG. 4 which can be coupled to the central body;

[0028]FIG. 7 a perspective representation of a further embodimentvariant of a valve in accordance with the invention;

[0029]FIG. 8 a perspective representation of the central body of thevalve in accordance with FIG. 7; and

[0030]FIG. 9 a perspective representation of the sealing part of thevalve in accordance with FIG. 7 which can be coupled to the centralbody.

[0031] In the perspective representation of FIG. 1, the blocking memberwhich can be inserted into the vent bore of the vulcanisation mould isdesignated generally with the reference numeral 1 and its blockingmember comprises, in accordance with this embodiment of the invention, acentral body 2 and a sealing part 3 which can be latched to it.

[0032] In accordance with FIG. 2, the central body 2 which preferablycomprises an injection-moulded part, is formed in the manner of acylindrical pin and is provided with guide grooves 18 uniformlydistributed around its periphery to receive clamping limbs 10 of thesealing part 3. Through the cooperation between the guide grooves 18 andthe clamping limbs 10 a security against rotation for the sealing part 3is also provided.

[0033] These guide grooves 18 are chamfered inwardly in the rear regionof the central body 2 and support projections 11 are formed in thegrooves 18 in the mould side end region of the central body 2 and servefor the latching of the sealing part 3. The guide grooves 18 are ledradially inwardly towards the end face 8 disposed at the mould side sothat inclined surfaces 19 arise.

[0034]FIG. 3 shows the sealing part 3 which preferably consists of thinspring steel and is formed by a circular surface region 4 forming ablocking surface on which three clamping limbs 10, which are uniformlydistributed over the circumference, are formed.

[0035] The blocking surface 4 is provided with a centrally disposedY-shaped slot aperture 7. The angling of the clamping limbs 10 from theblocking surface 4 takes place via short radial cuts 6 so that theregions of the clamping limbs 10 at the blocking surface side aredisposed radially somewhat within the outer periphery of the blockingsurface 4. Through these cuts and angled portions of the clamping limbs10, very narrow slots also arise, via which a certain air discharge cantake place, with the slots which result being so narrow that nopenetration of blank material occurs.

[0036] The clamping limbs 10 are provided with kinked locations so thatlimb parts project radially beyond the outer periphery of the circularsealing part 3 and the clamping limbs can thus take on the requiredfixation function in the state in which they are inserted into thebores.

[0037] A part region in the form of a coupling lug 5 is cranked inwardlyfrom each clamping limb 10 and this coupling lug 5 serves for thesnap-in latch connection to the central body 2.

[0038]FIG. 1 shows the assembled state of the central body 2 and thesealing part 3, with the clamping limbs 10 engaging into the guidegrooves 18 and the coupling lugs 5 latchingly engaging behind thesupport projections. If the so formed blocking member is pressed into amould bore, then the kinked regions of the clamping limbs 12 extend,whereby, on the one hand, the holding force for the blocking member inthe respective bore is produced and, on the other hand, the blockingsurface is stressed by the coupling lugs 5 against the end surface 8 ofthe central body 2.

[0039] If the blank material, i.e. the rubber material, reaches theblocking member 1 in the practical operation of a vulcanisation mould,which is provided with a large number of such blocking members, then theair, which is still present in the corresponding part regions of themould, can escape via the aperture 7 or via the cuts or gaps 6 havingvery small dimensions while the rubber material can at most enter intothe aperture 7, but can no longer penetrate into the minimal gap spacebetween the blocking surface 4 and the end face 8. Since the thicknessof the sealing part 3 only amounts to a fraction of a millimeter, hardlyvisible, minimal markings arise at most in practice due to penetrationof the blank material into the aperture 7 and are in no way disturbing.

[0040] As a result of the small thickness of the blocking surface 4, noadhesive forces can form between the walls of the aperture 7 and theblank material which could bring about a tearing of rubber material onopening of the mould and thus a blocking of the apertures. This is animportant reason why a problem-free long-term operation can be ensuredwith the blocking members of the invention.

[0041] The blocking members of the invention can be made practicallyfully automatically, with the sealing part 3 comprising a punched outand bent part and the central body 2 comprising a moulded orinjection-moulded part. The joining together of the two parts can alsobe automated as a result of the simple snap-in latch connection.

[0042] The second variant of the embodiment of the invention is nowdescribed by way of the two embodiments in accordance with FIGS. 4 to 9.

[0043] In the perspective representation of FIG. 4 the valve which canbe inserted into a venting bore of a vulcanisation mould is designatedwith the general reference numeral 2 and this valve 2 comprises acentral body 22 and a sealing part 23 which can be coupled to it.

[0044] The central body 22 is of substantially cylindrical shape and hasa plurality of strip-like clamping elements 30 distributed around itscircumference which, after the insertion of the valve into a ventingbore, clampingly contact the internal wall of the bore and form airpassages between them.

[0045] Supporting projections 31 are moulded on in the upper region ofthe central body, i.e. at the sealing side, which enable a coupling onof the sealing part 23.

[0046] The sealing part 23 is made in the form of a flexible sealingdisc, the surface 24 of which is elastically deformable in the directionof the central body in operation by the approaching blank surface.

[0047] The outer circumference of the sealing disc 23 contactscorresponding support surfaces 28 of the central body and it is providedcentrally with a circular cut-out 27 in the illustrated embodiment whichforms the main air throughflow opening. A disc-like formation 29 isprovided on the central body 22 lying opposite to this cut-out 27 and isof complementary shape. On deflection of the sealing surface 24 theformation 29 enters into the cut-out 27 and thereby practically closesthe main air throughflow opening.

[0048] A plurality of coupling limbs 25 are connected to the sealingdisc 24 distributed around the periphery but decoupled from itmotionwise by pairs of slots 26. The coupling limbs can be coupled inthe manner of a bayonet connection to the support projections 28 presentat the central body 22.

[0049] This type of coupling between the central body 22 and the sealingpart 23 only represents one possible type of coupling, it has, however,the advantage that a simple and rapid separation of the two parts ispossible by means of a suitable tool. For example a magnetic screwdriving tool can be used for this purpose.

[0050]FIG. 5 shows the design of the central body 22 with the formation29 provided centrally at the end face which cooperates with the cut-out27 in the sealing part 23. The support surface 28 at the end faceextends so that it drops away towards the formation 29 starting from itsperipheral region, so that the elastic sealing surface 4 can execute therequired closing and opening movements.

[0051] The radial height of the clamping elements 30 and also of thesupport projections 28 is so selected that the former can develop therequired clamping action in the venting bores and the latter enable acoupling to the coupling limbs 25 which takes place by a rotary movementeven with the central body 22 inserted into the venting bore.

[0052]FIG. 6 shows once again in detail the design of the sealing part23 or of the sealing disc with the central cut-out 27, the slot pairs 26and the coupling limbs 25, which have angled portions 32 at their freeends which engage behind the support projections 31 at the central body22 in the coupled state.

[0053]FIG. 7 shows a modified embodiment of the two-part valve 21, withthis embodiment being characterised above all by a further designsimplification.

[0054] The valve 21 in accordance with this embodiment again includes acentral body 22, in this case formed as a cylindrical pin, and also asealing part 23 which cooperates with the central body 22 and which isprovided with a plurality of corrugated spring limbs 35, in particularthree spring limbs which are formed in one piece and distributed aroundthe periphery, with the spring limbs being inwardly angled at their freeends 36 and thus defining a receiving space for the holding of thecentral body 22.

[0055] In contrast to the embodiment of FIGS. 4 to 6, the pin-likecentral body 22 no longer need be pressed into the venting bore of thevulcanisation mould. in this embodiment, but is rather simply held bythe spring limbs 35 of corrugated design. These corrugations on thelimbs 35 deform in the bore when being pressed in and press against thecentral body 22. In this manner this central body 22 is axially held inthe desired position, with the deformation stress of the limbs ensuringthat the elastic sealing disc 23 is held accurately positioned and canalso not be pressed out of the central body, with the bent-over freeends 36 additionally preventing the pin-like central body 22 fromsliding out of the receiving space formed by the corrugated springs 35.This type of holding is also of advantage because differences in growthin the bore and in the central body at elevated temperatures areautomatically necessarily compensated for by the pressing stressproduced via the corrugated springs 35.

[0056] The outer diameter of the sealing disc 23 is greater than thebore diameter, so that the outer peripheral edge of the sealing disc .23contacts the edge of the bore and can deform elastically in the axialdirection of the valve 21 starting from this contact surface. Moreover,the valve position is uniquely defined and the insertion is facilitatedby this abutment of the sealing part 23 at the respective edge of thebore.

[0057] The shape of the sealing part 23 which forms a sealing surfacecan be flat, can, however, also be of spherical shape, and indeed up toa spherical angle of about 20°.

[0058]FIG. 8 shows the central body for the valve of FIG. 7. Thiscentral body 22 has a smooth-walled peripheral surface 33 and isprovided at the end face which cooperates with the sealing part 23 witha chamfer 34 at its outer periphery.

[0059]FIG. 9 shows in a perspective view the cover or sealing part 23 ofthe valve of FIG. 7 and it can be seen that in this case a Y-shaped orgenerally star shaped cut-out 37 is arranged approximately centrally asthe main air throughflow opening. This design is not, however,essential; it does, however, ensure a problem-free operation inconjunction with the central body 22 of FIG. 8.

1. Vulcanisation mould for the manufacture of technical rubberproducts', in particular for the manufacture of vehicle tires,comprising a plurality of venting bores, in each of which there isprovided a blocking member, which at least substantially blocks thepenetration of blank material, characterised in that each blockingmember (1) includes a central body (2,22), in particular a pin-likecentral body (2, 22), which can be fixed in the respective venting borein a force-locked manner, and also a sealing part (23) connected to thecentral body (22), with the sealing part (23) having a surface region(4) at the inner side of the mould and substantially flush with it,which is provided with at least one aperture (7,27) and forms, togetherwith the mould side end face of the central body (2,22), at least oneflow path for the air following the aperture (7,27).
 2. Vulcanisationmould in accordance with claim 1, characterised in that the flow path ispronouncedly angled following the aperture (7, 27).
 3. Vulcanisationmould in accordance with claim 1, characterised in that the air flowpath is angled by approximately 90°, following the aperture (7.27) andcontinues between the bore wall and the central body (2,22). 4.Vulcanisation mould in accordance with one of the preceding claims,characterised in that the aperture (7, 27) is centrally arranged in thesurface region (4, 24) forming a blocking surface, and is of a roundbore and/or slot-like design, in particular in the form of a Y-slot. 5.Vulcanisation mould in accordance with one of the preceding claims,characterised in that blocking member is of two-part design, and in thatthe sealing part (3, 23) is latchably connected to the central body (2,22).
 6. Vulcanisation mould in accordance with one of the precedingclaims, characterised in that the central body (2, 22) is ofsubstantially cylindrical shape and has a smaller diameter in comparisonto the diameter of the venting bore, and in that the central body (2,22) can be fixed in the respective venting bore by clamping elements(10), which in particular consist of spring limbs, and which areprovided on the central body (2, 22) or on the sealing part (3, 23)while forming air passages.
 7. Vulcanisation mould in accordance withone of the preceding claims, characterised in that the sealing part (3,23) has a substantially disc-like or spherical blocking surface (4, 24)for blank material, having slot-like apertures (7, 27) and also includesa plurality of coupling lugs (5, 25) arranged distributed around theperiphery for the latching to the central body (2, 22).
 8. Vulcanisationmould in accordance with one of the preceding claims, characterised inthat the disc-like blocking surface (4, 24) has a plurality of radialcuts (6, 26) at the edge, in that in each case a pair of radial cuts (6,26) bound each clamping limb (10, 25), which is bent at right angleswith respect to the blocking surface (4, 24) and engages in a guidechannel (18) in the central body (2, 22).
 9. Vulcanisation mould inaccordance with claim 8, characterised in that the coupling lugs (5, 25)are formed from inwardly cranked sections of the clamping limbs (10, 25)and engage behind support projections (11, 13) at the central body (2,22).
 10. Vulcanisation mould in accordance with one or more of thepreceding claims, characterised in that the diameter of the pin-likecentral body (2, 22) lies approximately between 1 mm and 10 mm, and inparticular is approximately 0.01 mm to 2, mm smaller than the borediameter.
 11. Vulcanisation mould in accordance with one or more of thepreceding claims, characterised in that the sealing part (3, 23)consists of a sheet metal spring with a thickness in the range fromabout 0.05 mm to 0.3 mm.
 12. Vulcanisation mould in accordance with oneor more of the preceding claims, characterised in that the central body(2, 22) consists of an injection-moulded part.
 13. Blocking member inaccordance with one or more of the preceding claims for use invulcanisation moulds provided with vent bores.
 14. Vulcanisation mouldin accordance with claim 1, characterised in that the blocking memberforms a two-part valve (22); in that the blocking member has anelastically deformable surface region disposed at the inside of themould which cooperates in an at least substantially sealing manner withthe central body (22) on being loaded by the surface of the blank. 15.Vulcanisation mould in accordance with claim 14, characterised in thatthe central body (22) is of substantially cylindrical shape and has adiameter which is smaller in comparison to the diameter of the ventingbore; and in that the central body (22) can be fixed by clampingelements (30), which are provided on the central body (22) or on thesealing part (23), in the respective venting bore, while forming airpassages.
 16. Vulcanisation mould in accordance with claim 14 or claim15, characterised in that the sealing part (23) has a substantiallydisk-like or spherical sealing surface having cut-outs (26) and/orrecesses (27) and also a plurality of coupling limbs (25) distributedaround the periphery for the connection to the central body (22). 17.Vulcanisation mould in accordance with claim 16, characterised in thatthe disk-like or spherical sealing surface (24) is supported on thecentral body (22), in particular at the rim, and, on elastic deformationin the direction of the central body (22), comes into contact againstthe central body (22) with at least substantial closure of the airpassage openings.
 18. Vulcanisation mould in accordance with one of thepreceding claims 14 to 17, characterised in that a main air passageopening (27) is formed in the central region of the elastic sealingsurface (24).
 19. Vulcanisation mould in accordance with claim 18,characterised in that with the valve closed a complementarily shapedformation (29) of the cylindrical central body (22) engages into themain air passage opening (27).
 20. Vulcanisation mould in accordancewith one of the preceding claims 14 to 19, characterised in that thedisk-like elastic sealing surface (24) has a plurality of radial cuts(26), in that in each case a pair of radial cuts (26) bound a couplinglimb (25) which has a portion extending parallel to the peripheralsurface of the central body (22) and an angled free end (32) adjoiningit, with this coupling limb (25) cooperating with support projections(31) on the central body (22) in the manner of a bayonet connection. 21.Vulcanisation mould in accordance with claim 15, characterised in thatthe clamping elements (30) consist of strip-like formations, whichextend at least substantially over the axial length of the central body(22).
 22. Vulcanisation mould in accordance with one or more of theclaims 14 to 20, characterised in that the central body (22) has aformation free peripheral surface (33) and the clamping elements consistof corrugated spring limbs (35), which are formed in one piece with theelastic sealing disc (23) and which are preferably inwardly angled attheir free ends (36) to provide a receiving space for the central body(22).
 23. Vulcanisation mould in accordance with claim 22, characterisedin that the diameter of the sealing disc (23) is greater than thediameter of the venting bore.
 24. Vulcanisation mould in accordance withclaim 23, characterised in that the cylindrical central body (22) has achamfer (34) at its outer periphery at its sealing disc side, and thesealing disc (23) has a star-like cutout (17) at the centre. 25.Vulcanisation mould in accordance with one or more of the precedingclaims 14 to 24, characterised in that the valve diameter lies in therange from about 2 to 12 mm, and the diameter of the pin-like centralbody (22) is approximately between 0.1 and 2 mm, and in particularapproximately 0.7 mm smaller than the bore diameter.
 26. Vulcanisationmould in accordance with one or more of the preceding claims 14 to 25,characterised in that the sealing surface portion or the sealing disc(23) consists of a spring metal sheet, with a thickness in the rangefrom approximately 0.05 to 0.3 mm.
 27. Vulcanisation mould in accordancewith one or more of the preceding claims 14 to 26, characterised in thatthe sealing surface (24) of the sealing part (23) is substantially flator spherically shaped.
 28. Vulcanisation mould in accordance with claim27, characterised in that, with a spherical shape of the sealing surface(24), the angle of the spherical surface amounts to approximately 20°.29. Vulcanisation mould in accordance with on e of the preceding claims14 to 28, characterised in that the front surface of the central body(22) at the inner side of the mould has a flat, at least substantiallyconical recess.
 30. Vulcanisation mould for the manufacture of vehicletires having a plurality of venting bores, in each of which a valve ismounted and designed such that it is at least substantially closed bythe approaching surface of the blank and is opened again on demoulding,characterised in that each valve (21) is of two-part design and includesa central body (22), in particular a pin-like central body (22), whichcan be fixed in the respective venting bore, and also a sealing part(23), which is releasably connected to the central body (22) and whichhas at least one elastically deformable surface region (24) disposed atthe inner side of the mould, which cooperates in an at leastsubstantially sealing manner with the central body (22) on being loadedby the surface of the blank.